(a) Field of the Invention
The present invention relates to a system and method for detecting with an electric control unit (ECU) a misfire occurring in an engine cylinder. More specifically, the present invention relates to a system and method for detecting a misfire occurring in an engine according to drive mode status parameters, such as engine revolutions per minute (rpm) or load.
(b) Description of the Related Art
To prevent air pollution caused by the development of the automotive industry, exhaust gas emissions have been continuously restricted, and accordingly, techniques for electronically controlling engines have been developed.
Furthermore, as recent techniques for electronically controlling engines require the adoption of the On-Board Diagnosis 2 (OBD 2) standard that obligates a computer installed in a car to collect information needed to detect malfunctions and to generate alarms, systems and techniques to detect an increase of exhausted gas caused by a misfire and possibility the damage of catalysts are now required. Accordingly, a system and method for detecting an occurrence of a misfire and the cylinder at which the misfire occurred, and for the restoration of the proper operating status of the engine is now needed.
In a conventional system and method for detecting an engine misfire, when a piston moves back and forth between the top dead center (TDC) and bottom dead center (BDC) positions in a cylinder, the system measures the time required to achieve each predetermined rotation angle of a crank shaft. In this process, when an engine misfire occurs, the above noted time increases because of a decrease of an engine torque. At this time, the ECU compares a time variation ratio of this measured time with a predetermined reference value, and when the time variation ratio is greater than a predetermined reference value, a misfire is deemed to have occurred.
However, in the conventional system and method, a decrease of torque caused by an engine misfire does not immediately appear because of the mechanical characteristics of the system or inertia associated with various drive mode status parameters such as engine rpm or load. Therefore, the actual time variation ratio caused by the occurrence of the engine misfire is somewhat different from the time variation ratio detected at the ECU, and thereby, the generation of false detections or the failure to detect real engine misfires result. Especially during high-speed rotations of the engine, with a great amount of inertia at work, the changes of the torque caused by engine misfires do not quickly appear, and therefore, the possibility of failing to detect a misfire increases.